The present invention relates to toilet systems having removable waste holding tanks and in particular to a pressure relief vent for relieving internal pressure build-up within the waste holding tank.
Toilet systems have been developed in which a toilet bowl is removably coupled to a waste holding tank. Waste from the toilet bowl is flushed into the holding tank for storage until disposal at a later time. When the holding tank is filled with waste, it is removed from the bowl and carried to a disposal site where the contents are dumped from the tank.
Such a toilet system can be integrally formed in a recreational vehicle as shown in Assignee's U.S. Pat. No. 4,776,631. Alternatively, the toilet system can be a two-piece portable toilet such as that disclosed in Assignee's U.S. Pat. No. 4,145,773. These patents are hereby incorporated by reference.
The removable waste holding tanks disclosed in the above referenced patents include an inlet port through which waste enters the tank from the toilet bowl. The inlet port is equipped with a valve for closing the port when the toilet is not in use and for opening the port when waste is to be flushed from the toilet into the holding tank. The valve includes an appropriate seal to prevent the escape of odors from the tank and to prevent leakage during handling of the portable tank.
Once waste has accumulated in the holding tank, biological processes take place in the tank to begin the breakdown of the waste. These processes result in the production of vapor within the holding tank, increasing the tank pressure. The pressure within the holding tank may also deviate from the ambient pressure for various other reasons, such as travel to a higher altitude.
A pressure within the tank greater than the ambient pressure can create problems for the user of the toilet. For example, if a liquid, such as a chemical deodorant is introduced into the toilet bowl for flushing into the holding tank, a jet-like gas discharge from the holding tank through the liquid in the bowl may occur as the inlet port valve is initially opened, causing an upward spray of the liquid.
One solution to the problem of pressure build-up within the holding tank is to equip the tank with a vent that is operably coupled to the inlet port valve to open the vent before the tank inlet port is opened. Such a vent arrangement is shown in U.S. Pat. No. 4,776,631 referred to above. While in principal such a vent will relieve pressure from within the holding tank, in practice, insufficient venting often occurs before the inlet port is opened. This is due in part to the speed employed by the operator in opening the tank inlet port. Insufficient venting can result in the same problems encountered with an unvented tank.
Accordingly, it is one object of the present invention to provide an improved vent for a portable waste holding tank.
It is a further object of the present invention to provide a vent for a portable waste holding tank which is only operable to vent the tank when the tank is operatively coupled to the toilet bowl and not while the tank is being transported to a disposal site.
It is yet another object of the present invention to provide a waste holding tank vent that is normally closed to prevent diffusion of odors from the tank into the area surrounding the tank but which will operate to open and relieve small amounts of excess pressure as the pressure is generated.
The vent assembly of the present invention includes a valve body installed in a vent port in the holding tank wall having a vent passage therein for airflow from the tank interior to atmosphere. The valve body includes an upper valve seat surrounding the vent passage at the upper end thereof and an upper valve member is positioned upon the upper valve seat, covering the passage to seal the interior of the holding tank from the surrounding atmosphere. The only force acting to hold the upper valve member on the upper valve seat is gravity. The upper valve member is sufficient to prevent diffusion from the tank.
The bottom surface of the upper valve member is communication with the interior of the holding tank while the top surface of the valve member is in communication with the atmosphere. When the internal pressure in the holding tank exceeds the ambient pressure by a predetermined amount, sufficient to overcome the gravitational force acting on the upper valve member, the internal pressure will lift the upper valve member off the upper valve seat, allowing gas to be vented from the interior of the holding tank. The upper valve member will return by gravity to the upper valve seat, closing the vent passage, when the tank pressure is sufficiently reduced. By constructing the upper valve member to be light weight, only a small amount of gas will be vented each time the upper valve member is removed from its valve seat.
A lower valve seat is formed at the base of the vent passage and a lower valve member is provided for engagement with the lower valve seat to close the vent passage from the tank interior. The lower valve member is held in a closed, sealed position by a biasing spring. A release button is provided for opening the lower valve. The button is depressed by a cam on an upper portion of the toilet system containing the toilet bowl. When the tank is coupled with the toilet bowl, the release button is automatically depressed by the cam, opening the lower valve. The lower valve thus serves to seal the tank when the tank has been removed from the toilet bowl for dumping of its waste contents.
The lower valve member is also provided with a floatation device to raise the lower valve member against the lower valve seat if the tank is overfilled. This prevents spillage of waste through the vent assembly due to overfilling or splashing of the waste contents.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.